Compressor controlling mechanism



Dec. 1, 1931. F. D. HOLDSWORTH COMPRESSOR CONTROLLING MECHANISM Original Filed Nov 24, 1928 1474 82275021- H mil). IYOYdSaW/PZVM Patented Dec. 1, 1931 UNITED STATES PATENT orrlcr.

FRED D. HOLDSWORTH, OF CLAREMONT, NEW HAMPSHIRE, ASSIGNOR TO SULLIVAN MACHINERY COMPANY, A CORPORATION OF MASSACHUSETTS COMPRESSOR CONTROLLING MECHANISM Application filed November 24, 1928, Serial No. 321,744. Renewed June 18, 1931.

This invention relatesto mechanism for controlling a compressor, and more part cularly to mechanism for controlling the prime mover as the load of driving the compressor varies. invention relates to mechanism for controlling the speed of a prime mover by moving the throttle which controls the same.

In internal combustion engines, as now commonly designed, the speed of the engine is controlled by the regulation of the feed of the combustible mixture to the engine. Therefore, in order to keep the engine and the machine driven thereby up to speed, as

' the load increases, it is necessary to increase the volume of mixture fed to the engine. Accordingly, one object of my invention is to provide improved means for controlling the supply of explosive mixture to an internal combustion engine, as the demand made upon the same varies. A further and more specific object of my invention is to provide improved means for controlling the supply of explosive mixture to an internal combustion engine which is employed as the prime mover for an air compressor or other pumping device, 1ncreasing or decreasing the supply in accordance with the demands made by the compressor. Another object is to provide improved means for speeding up the compressor when the receiver tank pressure is reduced due to an excessive demand for air, so that the compressor will deliver an increased amount of air at the reduced pressure. A still further object of my invention is to provide improved means for varying the supply of fuel to the engine which drives an air compressor, in accordance with the loading and unloading of the compressor. A still further object is to provide improved means for varying the supply of fuel to the engine which drives an air compressor in accordance with the compressor discharge pressure, the relation between the compressor discharge pressure and the positioning of the engine throttle being so adjusted as to cause rapid opening of the throttle during the first increases in the discharge pressure. Other objects and ad vantages of the invention will be apparent In another and broader aspect my from the following description and more particularly pointed out in the claims.

In the accompanying drawings, in which for purposes of illustration one embodiment of my invention is shown,

Fig.1 is a side elevation of a compressor mechanism in which an illustrative embodiment of the invention has been incorporated.

Fig. 2 is a view in side elevation of the fuel supply control, a portion of the controlling mechanism being shown in section.

Fig. 3 is a section on line 33 of Fi 2.

Fig. 4 is a sectional view through t e intake and discharge valves of one cylinder of the compressor, the figure showing an unloading device which cooperates with the inlet valve.

In Fig. 1 of the drawings a portable comressor outfit is illustrated, the same com rismg a motor 7 and a compressor 8, 0th mounted on the frame 9 of a wheeled truck. The outfit is provided with a fuel tank 10, and a receiver 11 to which the air or other fluid being compressed is delivered by way of the connection 12. The compressor is provided with suitable inlet and discharge valve mechanism of which one set is disclosed in Fi 4.

mechanism is provided for unloading the compressor; and for purposes of illustration, a device for holding the inlet valve of one cylinder of the compressor off its seat is shown in Fig. 4. This figure shows a portion of one of the cylinders of the compressor with which cooperates a valve casing 13 within which is disposed a discharge valve 14 and an inlet valve 15. A cylinder 16 in the form of an inwardly projecting member 16 is formed integral with a cap 17 secured to the end of the valve casing 13. The cap 17 is perforated at 18 to permit the air to enter the valve casing. A piston 19 is reciprocable Within the cylinder 16; and the cylinder '16 and the piston 19 cooperate to act as a's ervomotor to which fluid under pressure is supplied by way of a pipe connection 20. The piston 19 carries a stud or bolt 21 which supports a pronged member 22. The prongs of the latter are adapted to engage the inlet valve 15, when the piston 19 is at the inner end of its travel within the cylinder 16. When the inlet valve is so engaged, it is lifted and held ofi' its seat, so as to unload the compressor in an obvious manner.

The engine 7 is provided with an intake supply connection 23 within which is disposed a power medium control member in the orm of a butterfly valve 24 (see Fig. 2). A fluid pressure responsive device 25 controls the same, being connected thereto by a link 26 whose end is bent laterally and adapted to be inserted in any one of a plurality of openings 27 in a lever 27. The movement of the pressure responsive device 25 is controlled by compressor discharge pressure acting on a piston opposing a compression spring so that equal increments of pressure will produce equal changes in the position of the device. Attention is particularly directed to the angular relation between link 26 and the lever 27. Due to this angle equal increments of pressure acting on the pressure responsive device will not produce equal changes in position of the lever 27 on account of the changing angularity between the link 26 and lever 27. On the other hand, the operation-is such that for an given movement of the link 26 during the first portion of the throttle opening a greater amount of rotation of lever 27 will take place than when the throttle is moved substantiallyto full open position. Similarly a drop in pressure from the maximum discharge pressure will produce very little change in the throttle open ing since the lever 27 is then nearly at right angles to link 26. The angularity of the connection between the link 26 and lever 27 may be adjusted to suit any particular set ofconditions by means of a turnbuckle'26'. For any articular throttle valve the angle which will be most suitable may be determined uite definitely and then a single-piece link su stituted for the three members which comprise link 26. The device 25 comprises a casing having a bore 28 of uniform cross section except where counterbores 29 and 30 are provi ed at the two ends. Within the bore 28 reccilprocates a member having two pistons 31 an 32 connected by a rod 33 which is formed midway of its length with an enlargement 34. As shown in Fig. 2 this enlargement 34 is formed integral with the rod 33; but it isobvious that the member 34 may be made separate and the rod 33 made in two parts and assembled with the member 34, if this be more convenient. A pin 35 is screwed into the enlargement 34 and is provided with a rounded head 36 to engage in a socket member 26" secured to the end of the link 26. A look nut 37 is provided for fastening the pin 35 in position. The pin 35 projects through a slot 38 in the side of the device 25. To provide for various adjustments of the throttle valve 24, a plurality of openings 27 are formed in the lever 27, and

the link 26 may connect with any one of these I openings 27, if necessary. It will be understood that the portion of the device 25 comprising piston 32, rod 33 and one end of cylinder 28 is in effect a servo-motor, while piston 31v provides a surface subject to compressor discharge pressure.

The pressure fluid connection for the fluid pressure responsive device 25 will now be described. A pilot valve 40 of a well-known type is connected by a short pipe 41 to an opening 42 into the bore 28 of the device 25. This pilot valve 40 is of the type which supplies fluid to the mechanism controlled thereby when the receiver pressure exceeds a predetermined maximum, and vents the mechanism to atmosphere when the receiver pressure falls a predetermined amount below such maximum. The connection from the receiver 11 to the pilot valve 40 is shown at 43, and delivers fluid at compressor discharge pressure to the pilot valve 40. A T 44 is provided in the pipe 43 so as to aflord a branch connection 45 to the pressure responsive device 25. This branch connection 45 is threaded into an opening 46 which communicates with the counterbore 29 in the device 25. The outer end of this bore 29 is closed by a plug 46 through which projects a screw 47, which acts as a stop member to prevent over-travel of the pistons 31 and 32.

As shown in Fig. 2 the piston 31 is toward the end of the bore 28 which is provided with the counterbore 29, and the piston 32 is disposed toward the other end of the device 25. The opening 42 in the bore 28 is disposed beyond the travel of the piston 32. To prevent over-travel of the piston 32 towards the right, there is provided a pin 48 whose position within the bore 28 is adjusted by a screw 49 projecting through a plug 50 which closes the counterbore 30. A spring 51 is interposed between the piston 32 and a flange 52 formed on the further end of the pin 48. It will therefore be noted that the pin 48 acts as a guide for the spring 51. An opening 53 is formed through the device 25 so as to open into the bore 28 between the opening 42 and the counterbore 30. A pipe 54 communicates with this opening 53, and leads to the pipes 20 of the unloading devices. It will be understood from the above description that pressure corresponding to the compressor discharge pressure acts upon the piston 31. So long as the compressor is loaded, the pilot valve 40 maintains the portion of the bore 28 between the piston 32 and the plug 50 in communication with the atmosphere. The spring 51 is therefore the sole pressure opposed to the pressure supplied through the connection 45 from the receiver. Accordingly, as the compressor discharge pressure increases, the pin 35 is moved further and further to the right (as shown in Fig. 2), the spring 51 being more and more compressed.

Should such a pressure be attained in the receiver as will causethe pilot valve 40 to unload the compressor, fluid is supplied through the connection 41 to fill the portion of the bore 28 to the right of piston 32. Due to the connection 54, fluid at receiver pressure is supplied to the unloading device through'pipes 20 and the compressor is unloaded. Meanwhile the pressure within the bore 28 beyond the piston 32, augmented by the spring 51, has moved the pin 35 promptly to the left, so as to cut down the speed of the motor.

As the fluid in the receiver 11 drops in pressure, the pressure in the pipe 43 likewise drops; and when the predetermined pressure for which the pilot valve 40 is set is reached, the fluid pressure in the bore 28 to the right of piston 32 is vented to the atmosphere, the pressure to the left of piston 31 remaining unchanged, however. This latter pressure is now opposed solely by the sprin 51; and, therefore, the pin 35 is move promptly to the right. Due to the connection 54, the pressure fluid within the cylinder 16 of the unloading device is vented to the atmosphere through pipes 20, pipe connection 54, bore 28, pipe 41 and the pilot valve 40. It is therefore evident that regardless of the pressure acting on the piston 31, when the pilot valve 40 operates to supply pressure to the right hand end of the cylinder, the compressor will be unloaded and the throttle valve moved to closed position, thus reducing the speed of the engine, and when the pilot valve operates to vent the right hand end of the cylinder, the compressor will be reloaded and the throttle valve opened.

In order to provide a sufficient throttle opening for starting the motor when the receiver tank is empty and the butterfly valve is in closed position, I have provided a rod 55 connected at 56 to the lever 27 and having a grasping portion 57 so that the throttle may be held open during cranking of the motor. When the motor has once been started, the control of the throttle may then be left to the automatic operation of the device 25.

The manner of functioning of my improved motor cont-rolling device should now be readily apparent. If the normal desired receiver tank pressure is around one hundred pounds per square inch and it be assumed that temporarily the demand for compressed air exceeds the normal output of the compressor running at full load speed, the receiver tank pressure will drop, for example, down to sixty, seventy, or eighty pounds. The load on the compressor will thereby be reduced a certain amount while of course the controlling device for the throttle valve will move a certain amount toward the closed position. However, due to the fact that the angle between" the link 26 and lever 27 is near a right angle and the throttle valve nearly wide open, there will not be a very large reduction in the power of the engine. Accordingly, there will be a surplus power at the lower air delivery pressure and so the tion in working pressure will compensate for, and with the supply of actuating medium being cut down faster than the load on the com ressor is dropping due to the decreasing disc arge pressure, the speed will begin to fa off, and when the discharge pressure is reduced to zero, the butterfly valve will ha re moved to substantially closed position, allowing only suflicient explosive mixture to ass to the engine to take care of the friction oad at slow speed.

Now, as more work in proportion is necessary to compress from zero to ten pounds than from fifty to sixty, say, the rapid action of the parts 26 and 27 is important in bringing the pressure up after the receiver has been emptied. Moreover, it is important that these parts be arranged so as to cut down the speed from the maximum value to the best full load speed at the desired full load. Both these results are well taken care of. .An increased demand for compressed fluid causing a pressure less than normal full pressure, and a consequent reduction of the load on the compressor, will cause a speeding up of the driving motor since its supply of power has not been proportionately reduced. This will enable the compressor and its driving motor to follow the demand for air due to the increased speed and attem t to maintain the pressure as high as possi le. When the demand for air is reduced to normal, the pressure will build up and the speed of the compressor will drop to normal ,full load speed. This will very often make it possible for a single machine or a smaller sized machine to meet the conditions satisfactorily on any given 'ob. The temporary periods of maximum emand for compressed air are usually not very long and a reduction of pressure say to seventy or eighty pounds would not be serious. The increased speed of the compressor at these working pressures would probably be suflieient to take care of the increased demand. Moreover, the extra large movements of the throttle at the lowest pressures will aid in pumping up the receiver to the desired line pressure.

While I have in this application specifically described one form which my invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration and that the invention may be modifled and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a controlling mechanism for a system comprising a driven element and an internal combustion engine for driving the same, in combination, a throttle valve for said internal combustion engine, a servo-motor controlled by said driven element for actuating said throttle valve, and operative connections between said servo-motor and said throttle valve comprising a pivoted member for actuating said valve, and an actuator member actuated by said servo-motor and pivotally connected to said pivoted member, the force exerted by said actuator member being directed at an obtuse angle to a line passing through the two pivot points of the pivoted member substantially throughout the range of operation of said servo-motor.

2. In a controlling mechanism for a compressor system comprising a compressor and a motor for driving the same, in, combination, a device for controlling the speed of said mocomprising a pivoted member, movement 0 which in opposite directions effects higher and lower speeds of said motor, and means for moving said pivoted member in opposite directions comprising a movable element having a surface subject to compressor discharge pressure, and a link pivoted to said pivoted member, said link being actuated by said element and said link and pivoted member being arranged to direct the actuating force exerted by said link at an obtuse angle to a line passing through the two pivot points of said pivoted member substantially throughout the range of operation of said servo-motor.

3. In a controlling mechanism for a compressor system comprising a compressor and an internal combustion engine for driving the same, in combination, a throttle valve for the fuel supply to said motor, a pivoted member for moving said throttle valve, and means for moving said member in opposite directions comprising a movable element having a surface subject to a compressor discharge pressure, and operative connections between said element and said member including an actuator pivoted to said member, the force exerted by said actuator being directed at an obtuse angle to a line passing through the two pivot points of the member substantially throughout the range of operation of said servo-motor.

4.. In a controlling mechanism for a compressor system comprising a compressor, an internal combustion engine for driving the same, and fluid pressure actuated mechanism for unloading the compressor, in combination, a throttle valve for the fuel supply to said motor, a pivoted member for moving said throttle valve, means for moving said member in throttle opening direction comprising a movable element having a surface subject to compressor discharge pressure, means for moving said member in throttle closing direction comprising a pressure fluid actuated servo-motor, a pilot valve for controlling the supply of actuating fluid both to the unloading mechanism and to said servo-motor, and operative connections between said pivoted member and said means for moving the same in throttle opening and closing directions including an actuator pivoted to said member, the force exerted by said actuator being directed at an obtuse angle to a line passing through the two pivot points of the member substantially throughout the range of operation of said servo-motor.

5. In a controlling mechanism for a compressor system comprising a compressor, an internal combustion engine for driving the same, and pressure fluid actuated mechanism for unloading the compressor, in combination, a throttle valve for the fuel supply to said motor, a pivoted member for moving said throttle valve, means for moving said member in throttle opening direction comprising a movable element having a surface subject to compressor discharge pressure, a

spring tending to move said element against compressor discharge pressure, means for moving said pivoted member in throttle closing direction comprising a servo-motor, a pilot valve for controllingsupply of actuating fluid both to the unloading mechanism and to said servo-motor, and operative connections between said pivoted member and said means for moving the same in throttle opening and closing directions including an actuator pivoted to said member, the force exerted by said actuator being directed at an obtuse angle to a line passing through the two pivot points of the member substantially throughout the range of operation of said servo motor.

6. In a controlling mechanism for a prime mover, the combination of a power medium control member, means responsive to an increasing load on said prime mover, and means for regulating the position of said power medium control member governed by said responsive means whereby for each additional increment of load said control member permits the flow of the power medium to the prime mover to be increased at a decreasing rate.

7. In a controlling mechanism for a prime mover, the combination of a power medium control member, means responsive to an increasing load on said prime mover, means governed by said responsive means including a movable element, and means for regulating the position of said power medium control member governed by said movable element whereby for a uniform movement of the latter sald power control memberis first moved at a relatively high rate and is subsequently moved at a slower rate.

8. The combination 'set forth in claim 6 furthercharacterized in that said responsive means includes a yieldable element and a member having a surface upon which fluid pressure is adapted to oppose movement by said yieldable means.

9. The combination set forth in claim 6 further characterized in that said means which is governed by the responsive means includes a plurality of connecting links so arranged as to effect a variable rate of movement of the final link.

10. The combination set forth 'in claim 6 further characterized in that the means governed 'by said responsive means includes a plurality of connected links, the final one of which is connected to the power control member which, substantially at its maximum open position, is disposed vertically and which during movement towards said vertical position moves at a decreasing rate for.

given uniform movement of said respons1ve means.

11. In a controlling mechanism for a prime mover, the combination of a power medium control member, means responsive to an increase in load on said prime mover including a movable element, and means for regulating the position of said power medium control member governed by said movable element, whereby for a given initial movement of said element said power control member is moved a predetermined amount, and during a further movement of the same given amount as before, said power control element is moved less than it was moved initially.

In testimony whereof I affix my si ature.

FRED D. HOLDSWO TH. 

